Ophiocordyceps sinensis is a kind of advanced nourishing precious traditional Chinese medicinal material, which contains a variety of nutrients and active ingredients comprising nucleosides, polysaccharides, sterols, fatty acids, proteins, polypeptides and volatile components, etc. It has the functions of anti-tumor, regulating immune system, promoting cellular repair, anti-free radicals, anti-oxidation, anti-aging, protecting myocardial and vascular cells, improving cardiovascular function, protecting liver, protecting kidneys, regulating respiratory system, regulating blood system and regulating blood lipids, etc.
Most Ophiocordyceps sinensis currently on the market are dried Ophiocordyceps sinensis; a large number of volatile components will evaporate in a process of drying Ophiocordyceps sinensis, part of the nutrition will be lost, active ingredients will be inactivated, and taking a substantial decline in taste. However, fresh Ophiocordyceps sinensis can maximize the retention of their nutrients and active ingredients, while maintaining its unique fragrance and crisp mouthfeel. The preservation of fresh Ophiocordyceps sinensis is an important problem at present, and the pre-cleaning procedures will affect the quality of preservation to a certain extent. A large number of parasites, heavy metals, pathogenic mildew and bacteria exist on the surface of freshly harvested fresh Ophiocordyceps sinensis, which cannot be completely cleaned by conventional methods, and therefore cannot be consumed directly. The cleaning method provides a basis for subsequent preservation. Methods regarding the processing and preservation of fresh Ophiocordyceps sinensis were disclosed, such as:
Chinese patent application (CN 102406164A) disclosed a method of processing fresh Ophiocordyceps sinensis and a method for preparing canned Ophiocordyceps sinensis, which mainly comprises storing cleaned fresh Ophiocordyceps sinensis at an ultra-low temperature of −70° C.; thawing and grading the fresh Ophiocordyceps sinensis; soaking the fresh Ophiocordyceps sinensis in tap water based preservation solution containing citric acid and sodium erythorbate; testing and sterilizing at a high temperature; and preparing canned Ophiocordyceps sinensis. 
Chinese patent for invention (CN 103740592B) disclosed a method of preserving the freshness of Ophiocordyceps sinensis, which disclosed that after washing the head, stroma and body of Ophiocordyceps sinensis respectively, the washed fresh Ophiocordyceps sinensis were soaked into an acidic 0.9% sodium chloride solution for 5-8 minutes in order to prevent loss of nutrients and active substances; and then the fresh Ophiocordyceps sinensis were cooled rapidly at −75° C. for 5-12 hours, and placed in a vacuum-freezer at −5-−25° C. for storage.
Chinese patent for invention (CN 102178226B) disclosed a method of processing fresh Ophiocordyceps sinensis, which mainly comprises refrigerating fresh Ophiocordyceps sinensis at a low temperature below −65° C.; setting up a method for cleaning and sterilizing using a combination of ultrasonic waves and ozone; and finally storing the fresh Ophiocordyceps sinensis at 0° C.
Chinese patent application (CN105199956A) disclosed a method of preserving the freshness of Ophiocordyceps sinensis, which mainly comprises washing Ophiocordyceps sinensis with a certain concentration of alcoholic solution; spraying honey water to cover the surface of the Ophiocordyceps sinensis to retain nutrition and moisture; conducting air drying and dehumidification, and quick-freezing at −30° C. and storing in a cold storage warehouse under −5° C.
Some of the above prior art preservation ideas include direct freezing at ultra-low temperature (−70° C.), some were quick-freezing (−30° C. to −75° C.) for locking active ingredients and storage at a low temperature (under 0° C.), and others, in order to retain nutrients and moisture or color, include the steps of soaking in acidic water or spraying honey water; these fresh Ophiocordyceps sinensis provided in the above prior art retained most nutrients and active ingredients compared with dry Ophiocordyceps sinensis products. However, when thawed for consumption, its freshness decreased significantly, even cell viability was lost. In addition, the Ophiocordyceps sinensis are softened and moistened, causing the appearance, mouthfeel and nutrition of these fresh Ophiocordyceps sinensis to be seriously affected. Meanwhile, soaking in acidic water and spraying with honey water would affect the original savory taste of fresh Ophiocordyceps sinensis. 
In order to retain the original nutrients and active ingredients, as well as freshness and mouthfeel after thawing for consumption, a fresh Ophiocordyceps sinensis product and a preparation method thereof are needed to maintain the appearance, color, nutritional value and mouthfeel, and to be able to be stored for a long time, thereby the preservation of freshness can really be achieved.